.app{
    .login{
        width: 100%;
        // 设置flex布局，子元素默认呈现一行
        display: flex;
        //子元素垂直居中
        align-items: center;
        //子元素靠左
        justify-content: flex-start;
        border: 1px solid black;
        background-color: aqua;
        #username,
        #password {
          height: .3rem;
          width: 2rem;
          border: none;
          border: 1px solid black;
          border-radius: .05rem;
          outline: none;
          margin: .1rem;
          padding-left: .1rem;
        }
        #submit{
           height: .3rem;
           width: .5rem;
        }
      }
    
}